At 4359mm long, 1786mm wide and 1557mm tall, the new B-class is 89mm longer, 11mm wider and 48mm lower than 2005’s first-gen model.

The altered dimensions have brought some crucial packaging changes. The front seats are 86mm lower than before and have a more upright position. At 976mm, rear legroom is said to surpass that of the S-class luxury saloon. Boot capacity is put at 666 litres, 121 litres more than before.

Inside, a high-quality dashboard carries design cues from the range-topping SLS. Among the new car’s many options is a free-standing colour monitor for the navigation and entertainment systems, including optional internet access.

The Mercedes MFA platform that underpins the B-class will also be used for the new A-class, CLC, GLC and selected Nissan models as part of the Daimler-Renault-Nissan alliance. The new structure replaces the previous model’s ‘sandwich’ platform, which boasted a flat floor.

A so-called M270 range of petrol engines at launch will be virtually all-new 1.6-litre turbocharged units, one making 121bhp and 147lb ft, and the other 154bhp and 184lb ft, with maximum torque in both available from just 1250rpm. The engines feature Mercedes’ third-gen direct-injection system and stop-start. These engines will soon be fitted to C-class and E-class models too.

The OM651 family of turbodiesels at launch will have a capacity of 1.8 litres. It will initially come in 107bhp/189lb ft and 134bhp/221lb ft states of tune.

Alongside the standard six-speed manual gearbox, a light, compact seven-speed, dual-clutch gearbox will be offered. Mercedes claims that this delivers nine per cent better economy than the CVT gearbox it replaces.